The present embodiments relate to interpolation for ultrasound imaging. In particular, velocity information is interpolated for multi-dimensional ultrasound imaging.
In diagnostic medical ultrasound imaging, velocities are estimated for spatial locations within a scan region. The region may be scanned using a polar coordinate format. The display format is frequently different than the scan format. To convert the scan data to data for display, the estimated velocities in the scan format are interpolated to provide estimated velocities in a display format.
Estimated velocities are typically provided as angular measurements. The angle is the phase of the first sample or first order coefficient of an autocorrelation function of echoes returned from a spatial location. The phase angle takes a value between π and −π in a unit circle. Any interpolation of a phase value accounts for the angular nature of the measurement or introduces undesired artifacts or errors. For example, a linear interpolation may result in an incorrect angle or phase determination. Angular position around the unit circle may be more accurately determined using a minimum arc interpolation. U.S. Pat. No. 5,429,137, the disclosure of which is incorporated herein by references, uses a minimum arc interpolation for two-dimensional scan conversion.
For display, velocity information is mapped to different colors. The hue of a color represents the direction and brightness or shade represents the magnitude of velocity. RGB or other color representations may be interpolated. However, interpolation of colors may produce colors outside of the velocity color map, resulting in user confusion.